CN115738155A - Spraying fire extinguishing optimization method for dealing with moving subway train fire - Google Patents
Spraying fire extinguishing optimization method for dealing with moving subway train fire Download PDFInfo
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Abstract
The application discloses a spray fire-extinguishing optimization method for dealing with a fire of a moving subway train, which comprises the following steps: acquiring the change rule of the air flow of the moving train in the moving-to-static process of the subway train; processing the change rule; judging the relation between the mechanical ventilation airflow and the change rule; obtaining an empirical formula of the air flow velocity of the moving train and an empirical formula of the ventilation quantity of the variable-frequency fan, which are obtained by back calculation of the speed per hour of the train; defining the Reynolds numbers of transverse flows of the air flow of the moving train and the mechanical ventilation air flow, the Reynolds number of the water mist field and the momentum ratio of the water mist field to the transverse air flow; and constructing a spraying system parameter optimization engineering model based on the Reynolds number of the transverse flow of the mechanical ventilation air flow, the Reynolds number of the water mist field and the momentum ratio of the water mist field and the transverse air flow, and using the spraying system parameter optimization engineering model to optimize the spray fire extinguishing of the subway train fire. The spraying system after optimizing has higher anti-interference characteristic, better fire extinguishing performance in this application, can adapt to the high-efficient demand of putting out a fire of motion train proruption conflagration.
Description
Technical Field
The application relates to the field of spray fire extinguishing optimization, in particular to a spray fire extinguishing optimization method for dealing with moving subway train fires.
Background
The subway operation mileage ranks first globally in China, and reaches 44 cities of China with built subway traffic systems in the end of 2020, and the total operation mileage exceeds 7000km. The subway brings convenience to public traveling, and meanwhile, attention to environmental problems and potential safety hazards is brought to the subway. Although the fire hazard frequency of the subway is relatively low, due to the geometric characteristics of narrow and limited space of the subway and the characteristic of high-density gathering of passengers in the subway, once the fire hazard occurs, if the fire hazard cannot be effectively controlled, serious casualties and economic losses can be caused.
The hazard of fire smoke is mainly due to three factors: high toxicity, high environmental temperature and low visibility. At present, only 1-2 fire extinguishers are generally equipped in subway carriages, but when a fire occurs, particularly in a carriage fire scene with more passengers, it is obviously unrealistic to look at the passengers in a hurry to start and use the fire extinguishers. After a fire occurs in a moving subway train, if active measures cannot be taken in the early stage to control the development of the fire in time, the irretrievable disastrous consequences can be caused. Especially when a fire hazard occurs in the running process of the train, the fire hazard can not only form cross-ventilation in the train to enlarge the fire range but also generate a remarkable piston wind effect when the train continues running, and fire smoke can spread along the moving direction of the train under the action of the piston wind until the whole train section is submerged, thereby seriously threatening the safety of passengers in the train.
Relevant researches show that tunnel piston wind is about 0.45 time of the train speed, tunnel temperature field change in fire mainly occurs in the train stopping stage, and CO concentration change mainly occurs in the train constant speed and braking stage. The cross wind has longitudinal continuity inside the running train and is greatly influenced by the change of the speed and the acceleration of the train. Obviously, the smoke diffusion law of a fire of a moving train is influenced by multiple factors of train cross-over wind, piston wind and mechanical ventilation of emergency response.
Spraying is the process of spraying a liquid through a nozzle into a gaseous medium, causing it to disperse and break up into small particle droplets. Due to the high speed movement of the liquid relative to the air or gas, or due to the application of mechanical energy and the rotation or vibration of the spraying device, the liquid can be atomized into fine particles of various size ranges. The atomized droplets must exchange heat and mass in the air due to evaporation. Evaporation necessarily absorbs heat from the surrounding air, thereby lowering the temperature of the surrounding air and effectively suppressing the fire in the event of a fire. The water mist fire extinguishing technology is greatly developed in recent years, and has the characteristics of no environmental pollution, quick fire extinguishing, low water consumption, small damage to protected objects and the like. In the existing spraying technology, a coping method that the spraying characteristics of the spraying system are influenced by airflow in the train moving process is not considered, actually, the flow, the atomizing particle size and the penetration distance of a spraying liquid beam are all influenced by the airflow generated by the train moving and the mechanical ventilation airflow of a tunnel, if the spraying system is used in the actual fire extinguishing process without optimizing the spraying characteristics of the spraying system in the airflow field, the effect is necessarily poor (such as fire sources cannot be covered, the spraying target deviates, and the like), and even negative effects (such as the visibility of evacuated people is greatly reduced) can be generated.
Disclosure of Invention
The application plans to implement the optimization to the water mist spraying system fire extinguishing performance when the moving train conflagration, and the key consideration is different to ventilate the coupling influence of smoke evacuation mode combination and moving train air current to the water mist field, and then optimizes the key parameter of spraying system.
In order to achieve the purpose, the application provides a spray fire-extinguishing optimization method for dealing with a moving subway train fire, which comprises the following steps:
acquiring the change rule of the air flow of a moving train in the process of moving the subway train to static;
processing the change rule;
judging the relation between the mechanical ventilation airflow and the change rule;
obtaining an empirical formula of the air flow velocity of the moving train and an empirical formula of the ventilation quantity of the variable-frequency fan by back calculation of the speed per hour of the train;
defining the Reynolds numbers of cross flows of the air flow of the moving train and the mechanical ventilation air flow, the Reynolds number of the water mist field and the momentum ratio of the water mist field to the transverse air flow;
and constructing a spraying system parameter optimization engineering model based on the Reynolds number of the transverse flow of the mechanical ventilation airflow, the Reynolds number of the water mist field and the momentum ratio of the water mist field to the transverse flow, and being used for optimizing the spray fire extinguishing of the subway train fire.
Preferably, the change rule comprises: the pressure and the air quantity of the piston air and the pressure and the air quantity of the draft air.
Preferably, the method for acquiring the change rule includes: and acquiring the pressure and the air quantity of the piston air and the pressure and the air quantity of the draft air based on a grid CFD technology.
Preferably, the method for processing the change rule includes: the pressure and the air quantity of the piston air and the pressure and the air quantity of the cross-ventilation air are described in the form of empirical formulas:
in the formula, Q s (t) is the time-varying air volume of the piston air or the draft air calculated by CFD, unit: m is 3 /s；
Average wind speed outside or inside the train calculated for CFD, unit: m/s; a. The T To calculate the cross-sectional area, the unit: m is 2 (ii) a v (t) is the time-varying additional wind speed calculated by the CFD; p (t) is the time-varying pressure caused by piston wind or draft wind calculated by CFD, unit: pa;
average pressure outside or inside the train calculated for CFD, unit:pa; p (t) is the time-varying additional pressure of the CFD calculation in units of: pa; lambda [ alpha ] 1 And λ 2 Are constants obtained by simulation.
Preferably, the method for determining the relationship includes: and judging whether the mechanical ventilation airflow and the moving train airflow are in a 'synergistic' effect, a 'superposition' effect or an 'antagonistic' effect.
Preferably, the method for obtaining the empirical formula of the air flow velocity of the moving train and the empirical formula of the ventilation volume of the variable frequency fan by back calculation of the speed per hour of the train comprises the following steps:
Q f ＝γ·V c ·A
in the formula, V c For moving train airflow rate, unit: m/s; v. of t Is train speed per hour, unit: m/s; β and n are parameters obtained by experiment; q f Is the ventilation volume of the variable frequency fan, m 3 S; a is the internal cross-sectional area of the train, m 2 (ii) a γ is a parameter obtained by experiment.
Preferably, the method for obtaining the reynolds number of the cross flow, the reynolds number of the water mist field and the momentum ratio of the water mist field to the cross flow comprises the following steps:
in the formula, re c Is transverse flow Reynolds number; d is the hydraulic diameter of the square cavity unit where the fire source is located, unit: m; rho c Is the air density of the square chamber unit, unit: kg/m 3 ；μ c Is the viscosity coefficient of air, in units: pa · s; u. of c The coupling velocity of the transverse air flow; re f The Reynolds number of the water mist field; d 32 Is the average diameter of the droplets Sauter, unit: m; q. q.s jet Volume flow rate of the spray system, unit: m is a unit of 3 /s；N f Is a water mist field; y is the momentum ratio of the water mist field to the transverse airflow; m c Momentum flux of the cross-flow; m is a group of f The momentum flux of the initial droplet group of the water mist field.
Preferably, the method for constructing the spray system parameter optimization engineering model comprises the following steps:
in the formula, l, k, j, h and s are fitting constants; y is the distance from the water mist outlet to the center of the liquid drop group in the vertical direction, and the unit is as follows: m; x is the distance from the water mist outlet to the farthest liquid drop in the horizontal direction, and the unit is: and m is selected.
Compared with the prior art, the beneficial effects of this application are as follows:
the method can optimize the performance of the train spraying system in the actual moving subway train fire process, so that the fine water spray field can effectively cover and efficiently extinguish the fire source in a coupling flow field formed by airflow generated by train movement and mechanical ventilation (opened after fire), and by determining the generation mechanism and the change rule of the airflow (piston wind and cross-over wind) in the moving subway train (from moving to static) process, clear the reasonable criteria of 'synergistic', 'superposition' or 'antagonistic' effect of different ventilation and smoke exhaust mode combinations and the moving train airflow and the maintenance method of the 'synergistic' effect, the characteristics of the fine water spray field and the control effect of the fine water spray field on the target fire source in different ventilation modes and train running states are obtained, and finally, the optimized spraying system key parameters (spray amount, spray pressure and spray hole diameter) are obtained. In addition, the spraying system after optimizing has higher anti-interference characteristic, better fire performance in this application, can adapt to the high-efficient demand of putting out a fire of motion train proruption conflagration, has promoted the perfection and the optimization of emergent scheme in this type of fire scene.
Drawings
In order to more clearly illustrate the technical solution of the present application, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for a person skilled in the art to obtain other drawings without any inventive exercise.
FIG. 1 is a schematic flow chart of a method according to a first embodiment of the present application;
FIG. 2 is a schematic diagram of a second embodiment of the present application;
fig. 3 is a schematic diagram of a two-dimensional simplified uniform acceleration linear motion of a single subway train in the second embodiment of the present application;
fig. 4 is a schematic diagram illustrating the variation law of the pressure and the air volume of the piston air and the cross air obtained in the CFD post-treatment process according to the second embodiment of the present disclosure;
fig. 5 is a schematic diagram of dimensionless fitting of shear layer structures in blended flow fields under different spray conditions and cross-flow conditions according to example two of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.
Example one
As shown in fig. 1, a schematic flow chart of a method according to a first embodiment of the present application includes the steps of: acquiring the change rule of the air flow of the moving train in the moving-to-static process of the subway train; processing the change rule; judging the relation between the mechanical ventilation airflow and the change rule; obtaining an empirical formula of the air flow velocity of the moving train and an empirical formula of the ventilation quantity of the variable-frequency fan by back calculation of the speed per hour of the train; defining the Reynolds number of transverse flow of the air flow and the mechanical ventilation air flow of the moving train, the Reynolds number of the water mist field and the momentum ratio of the water mist field and the transverse air flow; and constructing a spraying system parameter optimization engineering model based on the Reynolds number of the transverse flow of the mechanical ventilation air flow, the Reynolds number of the water mist field and the momentum ratio of the water mist field and the transverse air flow, and being used for optimizing the spray fire extinguishing of the subway train fire.
Wherein, subway train includes by the change law of the motion train air current to the quiet in-process of moving: the pressure and the air quantity of the piston air and the pressure and the air quantity of the draft air. The method for acquiring the change rule comprises the following steps: and acquiring the pressure and the air quantity of the piston air and the pressure and the air quantity of the cross air based on a grid CFD technology. The method for processing the change rule comprises the following steps: the pressure and the air quantity of the piston air and the pressure and the air quantity of the cross air are described in the form of empirical formulas:
in the formula, Q s (t) is the time-varying air volume of the piston air or the draft air calculated by CFD, unit: m is 3 /s；
Average wind speed outside or inside the train calculated for CFD, unit: m/s; a. The T To calculate the cross-sectional area, the unit: m is a unit of 2 (ii) a v (t) is the time-varying additional wind speed calculated by the CFD; p (t) is the time-varying pressure caused by piston wind or draft calculated by CFD, in units: pa;
average pressure outside or inside the train calculated for CFD, unit: pa; p (t) is the time-varying additional pressure of the CFD calculation in units of: pa; lambda 1 And λ 2 Are constants obtained by simulation.
The method for the relation of the mechanical ventilation airflow and the change rule comprises the following steps: and judging whether the mechanical ventilation airflow and the moving train airflow are in a 'synergistic' effect, a 'superposition' effect or an 'antagonistic' effect.
The method for obtaining the empirical formula of the air flow velocity of the moving train and the empirical formula of the ventilation quantity of the variable-frequency fan by back calculation of the speed per hour of the train comprises the following steps:
Q f ＝γ·V c ·A
in the formula, V c For moving train airflow rate, unit: m/s; v. of t Is train speed per hour, unit: m/s; β and n are parameters obtained by experiment; q f Is the ventilation volume of the variable frequency fan, m 3 S; a is the internal cross-sectional area of the train, m 2 (ii) a γ is a parameter obtained by experiment. The method for obtaining the Reynolds number of the cross flow, the Reynolds number of the water mist field and the momentum ratio of the water mist field to the transverse airflow comprises the following steps:
in the formula, re c Is transverse flow Reynolds number; d is the hydraulic diameter of the square cavity unit where the fire source is located, unit: m; rho c Is the air density of the square chamber unit, unit: kg/m 3 ；μ c Is the viscosity coefficient of air, unit: pa · s; u. of c The coupling velocity of the transverse air flow; re f The Reynolds number of the water mist field; d 32 Is the average diameter of the droplets Sauter, unit: m; q. q.s jet Volume flow rate of the spray system, unit: m is 3 /s；N f Is a water mist field; y is the momentum ratio of the water mist field to the transverse airflow; m c Momentum flux of the cross-flow; m is a group of f The momentum flux of the initial droplet population of the water mist field.
Finally, the method for constructing the spray system parameter optimization engineering model comprises the following steps:
in the formula, l, k, j, h and s are fitting constants; y is the distance from the water mist outlet to the center of the liquid drop group in the vertical direction, and the unit is as follows: m; x is the distance from the water mist outlet to the farthest liquid drop in the horizontal direction, and the unit is: and m is selected.
Example two
How the present application solves the technical problem in real life will be described in detail below with reference to the second embodiment. Fig. 2 is a schematic diagram of a specific implementation process of the second embodiment.
Firstly, the dynamic change rules of piston wind and cross wind in the moving-to-static process of the subway train, including the change rules of pressure and wind quantity of the piston wind and the cross wind, are obtained by a dynamic grid CFD technology. The dynamic mesh CFD technique is used to simulate that the boundary is rigid motion or is tangible, and that the computed basin shape is time-varying. In a dynamic mesh model, the mesh in the unsteady computational flow domain needs to be updated in every time step. In the second embodiment, the adopted dynamic grid method is a Local reconstruction (Local reconstruction) method. In this method, the deformation of the computational domain stresses or stretches the mesh near the motion boundaries, and when the distortion and size of the mesh do not meet specified criteria, the CFD will automatically reconstruct the mesh. Taking a two-dimensional simplified single-section subway train uniform acceleration linear motion as an example, as shown in fig. 3, in an initial stage of simulation, a grid near the tail of a train does not meet the torsion rate and size requirements and is reconstructed into a new grid, and meanwhile, the grid near the head of the train is gradually eliminated after being compressed. By parity of reasoning, the dynamic simulation of the uniform acceleration linear motion of the subway train in the tunnel is realized. The simulation of uniform deceleration (from moving to static) of the moving train is basically consistent with the process, but the difference is that an initial running speed is required for the train. Further, the pressure and air volume change rule of piston wind and cross wind can be obtained through the CFD post-treatment process, as shown in FIG. 4. The piston air is air flow formed by air in a train moving extrusion tunnel, the cross air is a carriage airtightness problem, so that a large pressure difference is generated among all parts in the carriage, and the air in the carriage flows under the action of the pressure difference. In the post-processing process, the piston wind counts the air volume and pressure of the outside of the train (in the tunnel) changing along with time, and the hall wind counts the air volume and pressure of the inside of the train changing along with time. The air volume and pressure of the two can be written as the following empirical formula:
in the formula, Q s (t) is the time-varying air volume of the piston air (draft) calculated by CFD, unit: m is 3 /s；
Average wind speed outside (inside) train calculated for CFD, unit: m/s; a. The T To calculate the cross-sectional area, unit: m is a unit of 2 (ii) a v (t) is the time-varying additional wind speed calculated by the CFD;p (t) is the time-varying pressure caused by the piston wind (draft) calculated by CFD, in units: pa;
average pressure outside (inside) train calculated for CFD, unit: pa; p (t) is the time-varying additional pressure of the CFD calculation in units of: pa; lambda [ alpha ] 1 And λ 2 Are constants obtained by simulation.
Then, comprehensively judging whether the combination of different ventilation and smoke exhaust modes (mechanical ventilation airflow) and the air flow of the moving train is a 'synergistic' effect (namely 1+1> < 2), 'superposition' effect (1 +1= 2) or 'antagonistic' effect (1 +1 <2). If the current mechanical ventilation airflow is the synergistic effect, the coupling effect of the current mechanical ventilation airflow and the moving train airflow (piston wind and cross-over wind) is shown to have an inhibiting effect (1 +1 >; if the effect is a superposition effect, the influence of the coupling effect of the current mechanical ventilation airflow and the moving train airflow on the fire smoke diffusion is negligible (1 +1= 2); if the effect is 'antagonism', the coupling effect of the current mechanical ventilation airflow and the moving train airflow has a promoting effect on the diffusion of fire smoke (1 +1 and less than 2), namely the smoke diffusion in the train is accelerated. Obviously, in the process of moving the moving train to the static state, if the mechanical ventilation airflow and the moving train airflow are required to maintain the synergistic effect all the time to suppress the fire, the mechanical ventilation adopts a variable frequency fan, and the ventilation quantity of the variable frequency fan is calculated through the moving train airflow velocity obtained by the reverse calculation of the train speed per hour.
The empirical formula of the air flow (piston wind and cross-over wind) and the flow velocity of the moving train which is inversely calculated by the speed per hour of the train is obtained through experimental data, and the empirical formula meets the following form:
in the formula, V c For moving train air flow (piston wind, cross-over wind) velocity, unit: m/s; v. of t Is train speed per hour, unit: m/s; β and n are parameters obtained by experiments.
The empirical formula for predicting the ventilation quantity of the variable frequency fan by the air flow velocity of the moving train is also obtained through experiments, and the empirical formula satisfies the following form:
Q f ＝γ·V c ·A (4)
in the formula, Q f For the air volume of frequency conversion fan, the unit: m is 3 S; a is the internal cross-sectional area of the train, unit: m is 2 (ii) a γ is a parameter obtained by experiment.
The lateral airflow (relative to the spray direction) resulting from the coupling of the piston wind, the draft wind and the mechanical ventilation airflow can be characterized by the cross-flow reynolds number:
in the formula, D is the hydraulic diameter of the square cavity unit where the fire source is located, unit: m; rho c Is the air density of the square chamber unit, unit: kg/m 3 ；μ c Is the viscosity coefficient of air, unit: pa.s; u. of c For the coupling speed of the transverse air flow (i.e. taking the air flow velocity V of the moving train into account c And mechanical ventilation wind speed Q f Airflow rate of/a), units: m/s.
In the second embodiment, for the mixing process of the water mist and the transverse air flow, the gas-liquid mixing flow field structures under different nozzle atomization states and transverse flow conditions are greatly different. In order to further analyze the influence of transverse airflow formed by coupling piston wind, cross wind and mechanical ventilation airflow on the water mist flow field, the Reynolds number Re of the water mist flow field is defined in the application f The number of water mist droplets N f (the flow of the fine water mist can be represented) respectively as follows:
in the formula (I), the compound is shown in the specification,D 32 is the average diameter of the droplets Sauter, unit: m; q. q.s jet Volume flow rate of the spray system, unit: m is 3 And s. Other parameter definitions are the same as in equation (5).
Wherein, the mixing of the water mist field and the transverse airflow is a complex multi-parameter two-phase flow process, and the change of the spraying state and the transverse flow condition can cause the obvious change of the shear layer structure. The shear layer structure is an important parameter for reflecting the structural characteristics (track) of the spray field and whether the fire source can be effectively covered, and the momentum ratio of the fine water spray field to the transverse airflow is defined as follows:
in the formula, M c Momentum flux of the cross-flow; m is a group of f The momentum flux of the initial droplet population of the water mist field. Both can be calculated by the following formulas:
in the formula, ρ w Is the density of water, unit: kg/m 3 ；u f The overall average velocity of the water mist droplets, unit: m/s.
According to dimensionless analysis, the expression of the shear layer structure can be obtained as follows:
in the second embodiment, fitting a dimensionless expression of a shear layer structure in a mixing flow field under different spray states and cross flow conditions by constructing a spray system parameter optimization engineering model includes:
in the formula, l, k, j, h and s are constants for data fitting; y is the distance from the water mist outlet to the center of the liquid drop group in the vertical direction, and the unit is as follows: m; x is the distance from the water mist outlet to the farthest liquid drop in the horizontal direction, and the unit is: m as shown in fig. 5.
From equation (12), it can be seen that in order to effectively cover the fire source with the shear layer structure of the spray, x and y need to be constrained, which can be achieved by controlling the spray volume (M) f ) Initial spray velocity (Y) and orifice diameter (Re) f ) And (5) realizing. In order to improve the control effect of the water mist field on the target fire source, the key parameter of the spray system is optimized through the formula (12) to be the core, a referable engineering method is provided for the optimization of the fire spray system of the moving subway train, and the time cost for optimizing the parameters of the spray system by adopting other methods such as CFD (computational fluid dynamics) is greatly reduced.
The above-described embodiments are merely illustrative of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements made to the technical solutions of the present application by those skilled in the art without departing from the spirit of the present application should fall within the protection scope defined by the claims of the present application.
Claims (8)
1. A spray fire-extinguishing optimization method for dealing with a fire disaster of a moving subway train is characterized by comprising the following steps:
acquiring the change rule of the air flow of the moving train in the moving-to-static process of the subway train;
processing the change rule;
judging the relation between the mechanical ventilation airflow and the change rule;
obtaining an empirical formula of the air flow velocity of the moving train and an empirical formula of the ventilation quantity of the variable-frequency fan, which are obtained by back calculation of the speed per hour of the train;
defining the Reynolds numbers of cross flows of the air flow of the moving train and the mechanical ventilation air flow, the Reynolds number of the water mist field and the momentum ratio of the water mist field to the transverse air flow;
and constructing a spraying system parameter optimization engineering model based on the Reynolds number of the transverse flow of the mechanical ventilation airflow, the Reynolds number of the water mist field and the momentum ratio of the water mist field to the transverse flow, and being used for optimizing the spray fire extinguishing of the subway train fire.
2. The method for optimizing spray fire extinguishment for coping with a fire of a moving subway train as claimed in claim 1, wherein said change law comprises: the pressure and the air quantity of the piston air and the pressure and the air quantity of the draft.
3. The method for optimizing spray fire extinguishment for a fire of a moving subway train according to claim 2, wherein the method for obtaining the change law comprises: and acquiring the pressure and the air quantity of the piston air and the pressure and the air quantity of the cross air based on a grid CFD technology.
4. The method for optimizing spray fire extinguishment for a fire on a moving subway train as claimed in claim 2, wherein said method for processing said law of change comprises: the pressure and the air quantity of the piston air and the pressure and the air quantity of the cross-ventilation air are described in the form of empirical formulas:
in the formula, Q s (t) is the time-varying air volume of the piston wind or the draft calculated by CFD, and the unit is as follows: m is 3 /s；
Average wind speed outside or inside the train calculated for CFD, unit: m/s; a. The T For calculating cross-sectional areaBit: m is 2 (ii) a v (t) is the time-varying additional wind speed calculated by the CFD; p (t) is the time-varying pressure caused by piston wind or draft wind calculated by CFD, unit: pa;
average pressure outside or inside the train calculated for CFD, unit: pa; p (t) is the time-varying additional pressure of the CFD calculation in units of: pa; lambda [ alpha ] 1 And λ 2 Are constants obtained by simulation.
5. A method for optimizing spray fire suppression for a moving subway train fire as claimed in claim 1, wherein said method of determining said relationship comprises: and judging whether the mechanical ventilation airflow and the moving train airflow are in a 'synergistic' effect, a 'superposition' effect or an 'antagonistic' effect.
6. The method for optimizing fire extinguishment by spraying on a fire on a moving subway train as claimed in claim 4, wherein said method for obtaining an empirical formula of air flow velocity of moving train and an empirical formula of ventilation volume of variable frequency fan based on back calculation of speed per hour of said train comprises:
Q f ＝γ·V c ·A
in the formula, V c For moving train airflow rate, unit: m/s; v. of t Is train speed per hour, unit: m/s; β and n are parameters obtained by experiment; q f Is the ventilation volume of the variable frequency fan, m 3 S; a is the internal cross-sectional area of the train, m 2 (ii) a γ is a parameter obtained by experiment.
7. The method for optimizing fire suppression through mist spraying on a fire of a moving subway train as claimed in claim 6, wherein said method for obtaining Reynolds number of said cross flow, reynolds number of said water mist field and momentum ratio of said water mist field to cross flow comprises:
in the formula, re c Is transverse flow Reynolds number; d is the hydraulic diameter of the square cavity unit where the fire source is located, unit: m; rho c Is the air density of the square chamber unit, unit: kg/m 3 ；μ c Is the viscosity coefficient of air, in units: pa.s; u. u c Is the coupling velocity of the cross-flow; re f The Reynolds number of the water mist field is; d 32 Is the average diameter of the droplets Sauter, unit: m; q. q.s jet Volume flow rate of the spray system, unit: m is a unit of 3 /s；N f Is a water mist field; y is the momentum ratio of the water mist field to the transverse airflow; m c Momentum flux of the cross-flow; m f The momentum flux of the initial droplet population of the water mist field.
8. The method for optimizing spray fire extinguishment for a moving subway train fire according to claim 7, wherein the method for constructing the spray system parameter optimization engineering model comprises:
in the formula, l, k, j, h and s are fitting constants; y is the distance from the water mist outlet to the center of the liquid drop group in the vertical direction, and the unit is as follows: m; x is the distance from the water mist outlet to the farthest liquid drop in the horizontal direction, and the unit is: and m is selected.
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| CN108760354A (en) * | 2018-05-22 | 2018-11-06 | 中南大学 | Train carries analog detection method, system and the medium that burning things which may cause a fire disaster operation flue gas transports |
| CN109163872A (en) * | 2018-09-30 | 2019-01-08 | 东北大学 | A kind of water mists control the experimental provision and method of damp and hot wind long and narrow space fire |
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| CN118070569A (en) * | 2024-04-19 | 2024-05-24 | 中铁建大桥工程局集团第三工程有限公司 | Comprehensive optimization system and method for ventilation calculation of high-altitude tunnel |
| CN118070569B (en) * | 2024-04-19 | 2024-07-12 | 中铁建大桥工程局集团第三工程有限公司 | Comprehensive optimization system and method for ventilation calculation of high-altitude tunnel |
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| CN115738155B (en) | 2023-08-29 |
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